1. Field of the Invention
The present invention relates to a knee protecting air bag system in which an air bag housed on a lower side of a body side member such as an instrument panel is inflated so as to protect the knees of an occupant.
2. Description of the Related Art
A conventional knee protecting air bag system includes an air bag that is folded to be housed in a housing portion on a lower side of a body side member such as an instrument panel that lies in front of an occupant seated in a driver's or a front passenger's seat (for example, refer to JP-A-2002-337642 and JP-A-2005-75143). As portions that deploy to inflate towards the rear from the housing portion by introducing inflation gas thereinto, this air bag includes an upper inflating portion that deploys to inflate to an upper side of the housing portion to protect the knees of the occupant and a lower inflating portion that deploys to inflate to a lower side of the housing portion to thereby be disposed at the rear of the body side member. This air bag also has an occupant side wall portion that is disposed on a side facing the occupant and a body side wall portion that is disposed on a side facing the body side member when the air bag completes its inflation. Additionally, the air bag has a plurality of thickness controlling tethers that connect the occupant side wall portion and the body side wall portion when the air bag completes its inflation.
In the conventional knee protecting air bag system, however, when the upper inflating portion of the air bag deploys to inflate upwards from the housing portion as a result of the air bag system being activated, although the thickness of the air bag is controlled by the tethers, in case the air bag deploys to inflate while being spaced apart to the rear from the body side member, the air bag has difficulty in entering a narrow space defined between the knees of the occupant and the body side member.